The shunt resistor is used for observing battery current of electrical charge and discharge so as to prevent the battery trouble beforehand. The shunt resistor is excellent in current detection accuracy, small in current drift, and even if a large current is applied, excessive heat is not generated. The shunt resistor is used in a field where super-low resistance value is required, and for instance, a shunt resistor of plate-shape has been proposed (refer to Japanese laid open patent publication H6-224014).
In case of detecting high frequency current, the plate-shaped resistance body shown in the patent publication, is unsuitable for detecting an accurate current, since skin effect may appear comparatively from early stage of low frequency. That is, as shown in left figure of FIG. 1, high frequency current C flows by skin effect at part in corner of resistance body 11 shown by hatching, and the current becomes difficult to flow at central portion of the resistance body. Accordingly, resistance value rises since effective area of high frequency current flowing decreases. Therefore, accurate detecting current becomes difficult upon the current including high-frequency component.
Even in case of making cross-section of resistance body 11 circle-shaped as shown in right figure of FIG. 1, high frequency current C concentrates at outer part shown by hatching in the figure by skin effect, and resistance value changes. Furthermore, change of resistance value is fewer in case of cross-section of resistance body circle-shaped than that of rectangle-shaped.